Adds optional timeout for AJAX POST requests.
Adds optional timeout for AJAX POST requests.

Allows calls to override the default 60 second timeout for POST requests
which are likely to take more than a minute to complete. Should only be
used in rare cases, and not as a workaround for a performance issue.

rapid7/nexpose-client,jhart-r7/nexpose-client,tomhart-r7/nexpose-client,gschneider-r7/nexpose-client,nbirnel/nexpose-client